I just picked up a used keystoker koker in good condition and am faced with the decision of how to vent. The stove came with a direct vent, however I would like to use my chimney as it is there not being used. My concern is that it is an old chimney with a terra cotta liner and the liner looks to have some wear and some cracks where a hole was opened up near the bottom. I would like for the coal stove to be as safe as possible and my concern is CO gas. I don't want to do a SS liner since they don't seem to last with coal. The direct vent is an option however it is more work to install and more maintenance. I don't have much experience with chimneys so someones opinion with some experience would be great. Attached are some pics up the flue. I am going to get up on the roof this weekend and give it a brushing and see what it looks like from the top.

I wouldn't hesitate to use that stack. It looks like a good interior stack well built. Older tile liners may not have been properly vitrified and thus you sometimes see some flaking internally; a few vertical cracks in a tile liner in an otherwise sound chimney isn't a safety issue with coal. CO doesn't leak out of a stack, it's under negative pressure, this is a myth propagated by idiots and those who wish to take your money to reline every chimeny with a nick, scrape, or small crack in the liner.